Production of gasoline



V Patented Feb. '4, 1941 raonuo'rron or GASOLINE Alexis Voorhies, Jr., Baton Rouge, La., asslgnor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application May 31, 1939, Serial No. 276,611

This invention relates to the production of motor fuel of the gasoline type from higher boiling hydrocarbons and pertains more particularly to a method of producing aviation gasoline.

It has heretofore been proposed to crack high-' er boiling hydrocarbons into lower boiling hydrocarbons suitable for motor fuel by passing the hydrocarbons to be cracked through a cracking zone containing a catalyst such as naturally active or activated clay or certain synthetic adsorbent gels containing silica and alumina. The

catalytic cracking process when carried out according to previous methods produces gasoline of relatively high octane number. This product, however, normally contains a highpercentage of unsaturated constituents which gives it an abnormally high acid heat. 1

The acid heat test is a common method for determining the unsaturated content of gasoline and is described, for example in vol. IV of "Science of Petroleum, page 2430 (publishedby, the

Oxford University Press). According to this test, 7

the acidheat number is expressed as the number of degrees Fahrenheit rise in temperature,

following the addition of cos. of 66 B. sulphuric acid to 150, ccs. of fuel to be tested ina Thermos flask. The mixture is thoroughly -8 tated and the temperature. rise during a three minute period following the addition of the acid 30 is expressed as the acid. heat. Abnormally high acid heat numbers are considered objectionable in many cases particularly in gasoline for aviation service.

In order to meet acid heat specifications for aviation-gasoline, it has heretofore been considered necessary to subject the raw catalytically cracked gasoline distillate to furtherv refining treatment such as with clay or sulphuric acid or to subject the distillate to a mild hydrogenating 40 treatment in order to reduce the unsaturated content/ of the product. The refining treatment with clay or sulphuric acid, in addition to increasing the cost of the operation, materially reduces the yield of gasoline recovered since substantial amounts, amounting in some cases to as high as 10% of the total product, are removed during the refining process. Hydrogenation, on the other hand, in most cases results in loss of octane number inaddition to the increase in cost of production of the desired product.

One of the primary objects of the present invention is to provide a method for producing gasoline, particularly gasoline for aviation service in a simple and more inexpensive manner.

A further related object of the invention is to provide a method of producingaviation gaso-,- line which will meet the required acid heat specifications without sacrifice in yield or in reduction of octane number thereof.

I have found that by the proper selection of 5 feed stock, catalysts and cracking temperature,

it is possible to produce a finished gasoline having a high octane number, good lead susceptibility and low acid heat with little if any further refining treatment required. l0 The-feed stocks employed according to the present invention should :contain a major percentage of constituents boiling below 600" F., or

in other words have a mid-boiling point below 600 F. and have an aniline point'below 155 F. l5

and preferablybelow F. For purposes of the present invention the boiling range and aniline point areto-a certain extent reciprocal in i that the higher the mid-boiling point the lower 20 should be the aniline point.

The catalyst employed in carrying out the cracking is preferably a synthetic gel comprising silica and alumina. One particularly eflective method of producing the catalyst is to first react a sodium silicate solution with an acid 25 under carefully controlled conditions to form a hydrosol which later sets into a hydrogel. The

hydrogel so formed may be broken up, washed free of reaction salts and impregnated with aluminum nitrate or other decomposable salts, of aluminum. The impregnated hydrogel may" be slowly dried and thereafter activated ata temperature of about 800 F. to decompose the aluminum salt and activate the catalyst. It will be understood, however, that the invention in 35 its broader phases is not restricted to this particular method of producing synthetic silicaalumina .gels.

The cracking operation should be carried out at relatively low temperatures, for example be- '40 tween 700-80.0 F. and preferably about 750 F.

As a guide in carrying out the process in accordance with the present invention, to obtain the best results thereof, the following comparative examples may be helpful. It will be 'under- 45 stood, however, that the values and conditions given therein are illustrative rather than limitive.

Example 1 per volume of catalyst per hour for one-half hour cracking periods between regenerations. The reaction zone was maintained at a temperature of 750 F. and the catalyst employed was a synthetic gel of silica and alumina formed by impregnating silica hydrogel with a solution of aluminum nitrate and thereafter drying and decomposing the aluminum nitrate and activating the gel. The resulting catalyst had a molar ratio of silica to alumina of about 12:1. Theresulting cracked products were fractionated to separate aviation gasoline having an. end point of 303 F., the said aviation gasoline amounting to 25.9% of the feed charged to the process. The resulting aviation gasoline had an acid heat of F., a clear octane number (A. S. T. M.) of 81.0 and an octane number of 91.7 with the ad.- dition of 3 cos. of tetraethyl lead per gallon of fuel. A more complete inspection of the resulting product is given in the table appearing hereinafter.

' Example 2 A 17% top fraction of Miranda crude having an A. P. I. gravity of 35.1, an aniline point of 118 and a boiling range between 244 F. and 507 F. was passed through a catalytic cracking zone, containing the same type of catalyst described irr Example 1. The rate of feed of the oil to be cracked through the catalytic cracking zone was 0.3 volume of liquid feed per volume of catalyst per hour and the length of the cracking periods between regeneration was 30 minutes. The reaction zone was maintained at a temperature of 725 F.

The cracked products were fractionated to separate an aviation gasoline having an end point of 308 F. The amount of aviation gasoline so produced was 30.8% of the fresh feed. The resulting aviation gasoline'had an acid heat of 8 F. and an A. S. T. M. octane number of 79.2 clear and 89.5 with the addition of 3 cos. of lead per gallon of fuel.

F. and a boiling range of 365-830 F. when testedunder the same conditions described in Example 1 yielded 24.1% of 280 end point aviation gasoline having an octane number of 78.3 and an acid heat of F. E

Example 4 A 95% top fraction of a visbreaker gas oil having an A. P. I. gravity of 29.6, a boiling range of 400-687 and an aniline point of 131 when tested under conditions described in Example 1 yielded 24.5% of 283 F. end point aviation gasoline having an octane number of 76.8 and an acid heat of 20+ F. 7

Example 5 An East Texas gas oil having an A. P. I. gravity of 33.7, an aniline point of 173 F. and a boiling range between 515 and 681 F. was tested under the conditions, described in Example 1. The resulting product was fractionated to separate a gasoline having an end point of 334 F. The aviation gasoline so produced had an acid heat of 34 as compared with 12.5, 8, 16.5 and 21 for Examples 1 to 4 respectively.

Example 6 An East Texas kerosene having an A. P. I. gravity of 43.2", an aniline point of 145 F. and a boiling range between 315 and 546 when tested under conditions described in Example 1 gave 20.1% of an aviation gasoline having an end point of 289 and an acid heat of 16.

Comparing this example with Example 5 it will be noted the boiling range andaniline point i are important factors in producing a gasoline of low acid heat.

Example 7 To determine the effect of temperatur the same feed stock described in Example 4 was tested in the same manner as described in Example 1, except that the temperature was raised to 850 F. and the feed rate ,was increased to 1.2 volumes of liquid feed per volume of catalyst per hour to obtain substantially the same conversion. In this test 20.6% of 294 F. end point aviation gasoline was produced having an acid heat of 70 F. as compared with 20+ in Example 4.

A more complete detailed inspection of the products produced in Examples 1 and 3 to 7 inclusive are given in the following table:

Example 1 3 4 5 6 7 Catalyst Sim-A1103 gel. SiOz-AlzO; gel. Slog-A1103 gel. SiOg-AlzOa g0]. Slog-A1203 g0]. SiOz-AlzOz g0].

17% top 90% top vis B E. Texas E. Texas vis B Mir-crude. Mir-crude gas oil gas oil kerosene gas oil Feed:

Mid. B. P 336-540 365-830 400-687 515-681 '420 400-687 Aniline point, F 114 123 131 173 145 131 A. P. I. gravity 34. 1 25. 0 29. 66 33. 7 43. 2 29. 6 Operating conditions:

Feed v./v./hr 0. 6 0. 6 0.6 0. 6 0.6 l. 2 Cracking cycle hours /6 54 $4 /5 V Tern erature, F. 750 750 750 750 750 850 Yiol percent feed. 25.0 24. 1 22. 0 Gasoline inspection:

P. I. gravity 62. 5 Color Saybolt. +12 Aniline point 97 Corrosion-cu. dish D N P Gumcu. dish (mgs. l5. 7 Doctor Pass Breakdown, hours Acid heat 0 Vapor pressure (Roid).. 1. 4 A. S. '1. 80. 2

taining pentanes and lighter amounting to 8.7%

The aviation gasoline prepared according to the present process has been found to contain only a relatively small quantity of aromatic hydrocarbons, most of which appear in the higher boiling fractions (toluene range). The product does, however, contain a high percentage of iso paraifins amounting to about The process, when carried out according to the present invention, not only produces high grade aviation motor fuel, but also produces a higher boiling fraction which has excellent anti-knock properties and can be employed either as a safety fuel, as a blending agent for low octane gasoline or as a solvent.

For example, the total cracked products prepared in Example 2 were separated into the following fractions (1) a lightgaseous fraction conof the total feed, (2) an aviation gasoline fraction amounting to 25.9% of the fresh feed as previously described, (3) a heavy naphtha fraction boiling between 300-400 F. amounting to 37.5% of the feed and (4) a heavier gas oil fraction amounting to 25% of the feed.

The heavy naphtha fraction had an A. P. I. gravity of 35.9, an aniline point of 80 R, an Abel Flash point of 112 F. and a clear A. S. T. M. octane number of 75.8.

Having described the preferred embodiment and given specific examples thereof, it will be understood that my invention embraces such other variations and modifications as come within the spirit and scope thereof. It will be further understood that it is not my intention to unnecessarily limit the invention except as necessary to distinguish from prior art.

I claim:

1. A method of making gasoline having a high octane number and low acid heat which comprises passing an oil having an aniline point below 155 F. and a mid boiling point below 600 F. through a cracking zone in contact with a catalyst comprising silica and alumina, maintaining said cracking zone at a temperature between 700-800 F. and thereafter separating a gasoline fraction from the cracked products.

' 2. A method of preparing gasoline having a high octane number and low acid heat which comprises passing an oil having an aniline point below'155 F. and a mid .boiling point below 600 F. through a cracking zone containing a catalyst comprising silica and alumina, maintaining said cracking zone at a temperature between about 700 and 800 F. and thereafter separating a gasoline fraction from the resulting cracked products.

3. A method of preparing gasoline having a high octane number and low acid heat which comprises passing an oil having an aniline point below 155 F. and a mid boiling point below 600 F. through a cracking zone containing a catalyst compirising silica and alumina in which the molar ratio of silica to alumina is about 12 to 1, maintaining said cracking zone at a temperature between 700 and 800 F. and there-after separating a gasoline fraction from the resulting cracked products.

4. A method of preparing gasoline having a high octane number and low acid heat which comprises passing an oil having an aniline point below 155 F. and a mid boiling point below 600 F. through a cracking zone containing a synthetic gel comprising silica and alumina formed by combining the alumina with the silica while the latter is in hydrous state, maintaining said cracking zone at a temperature of about 700 and about 800 F. and thereafter separating the gasoline fraction from the resulting cracked products.

5. A method of preparing gasoline having a high octane number and low acid heat which comprises passing an oil having an aniline point below.l55 F. and a mid boiling point below 600' F. through a cracking zone containing a synthetic gel comprising silica and alumina formed by impregnating a hydrous-oxide of silica with a decomposable salt of alumina and thereafter drying the hydrous oxide and decomposing the aluminum salts, maintaining said cracking zone at a temperature between about 700 and 800 F. and thereafter separating the gasoline from the resulting cracked products.

6. A method of preparing aviation gasoline having a rel atively low end point, low acid heat and high octane number which comprises passing an oil having an aniline point below 155 F. and a mid boiling point below 600 F. through a cracking zone' containing a synthetic gel comprising silica and alumina, maintaining said reaction zone at a temperature between about 700 and about 800 F. and thereafter separating the gasoline from the resulting cracked products.

7. A method of producing aviation gasoline having a relatively low end point, a low acid heat and a high octane number which comprises passing an oil having an aniline point below 150 F. and a mid-boiling point below 600 F. through a cracking zone containing a synthetic gel comprising silica and alumina formed by impregnating silica hydrogel with aluminum nitrate solution and thereafter drying and decomposing the aluminum nitrate, maintaining said cracking zone at a temperature between about 700 and about 800 F. and thereafter separating the gasoline from the resulting cracked products.

ALEXIS VOORHIES, JR. 

